<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
	<title>absolute</title>
	<style>
	    .box1{
		    background-color:red;
			height:120px;
			width:120px;
			position:absolute;<!-- 脱离文档流-->
		}
		.box2{
		    background-color:blue;
			height:240px;
			width:240px;
			margin-bottom:20px;<!--未脱离文档流-->
		}
		.box3{
		    background-color:green;
			height:120px;
			width:120px;
			position:absolute;<!-- 脱离文档流-->
		}
		.box4{
		    background-color:pink;
			height:240px;
			width:240px;
			position:absolute;<!-- 脱离文档流-->
		}
	</style>
</head>
<body>
    <div class="box1">box1红色</div>
	<div class="box2">box2蓝色</div>
	<div class="box3">box3绿色</div>
	<div class="box4">box4粉色</div>
</body>
</html>